docstr: Prepare possibly enhanced waveforms
docstr_tok: ["Prepare","possibly","enhanced","waveforms"]
code: def prepare_wavs(self, signal, stage):
      """Prepare possibly enhanced waveforms"""
      wavs, wav_lens = signal
      # Add waveform augmentation if specified.
      if stage == sb.Stage.TRAIN and hasattr(
          self.hparams, "wav_augment"
      ):
          wavs, wav_lens = self.hparams.wav_augment(wavs, wav_lens)
      return wavs, wav_lens
  
imports: import os
  import sys
  import torch
  import torchaudio
  import logging
  import speechbrain
  from pesq import pesq
  from pystoi import stoi
  from composite_eval import eval_composite
  from hyperpyyaml import load_hyperpyyaml
  from speechbrain.utils.data_utils import undo_padding
  from speechbrain.utils.distributed import run_on_main, if_main_process
label_desc: Use image node_id 2 for calling the MTLbrain obj's underlying member method code with example usage: obj.prepare_wavs(signal, stage) and returns: wavs,  wav_lens